Modern innovation allows us to tap into the wonders of chemistry at the nanoscale level. The spontaneous formation of self-assembled monolayers and thin films at the solution-solid interface are driven by a fine balance of intermolecular forces. The electronic, optical, and mechanical properties of these thin films can be dramatically affected by the nature of the first layers of material in contact with its support - often an electrode. Therefore, understanding the formation kinetics and thermodynamics of the first monolayer is highly desirable. The growth of the non-covalent self-assembly of Co(II) octaethylporphyrin at the solution-Au(111) and solution-HOPG interface is presented. The dramatic roles that the choice of substrate and organic solvent play give insight into the balance of the intermolecular forces driving the self-assembly. A pseudo-hexagonal structure was observed in the porphyrin adlayer when solvents decane or 1-phenyloctane were used. Under toluene or 1,2,4-trichlorobenzene, pseudo-polymorphism was observed where both rectangular and pseudo-hexagonal structures were present. The stability of these rectangular structures (before undergoing a phase transition into the pseudo-hexagonal structures) differed significantly and were also highly dependent on the substrate used. Real-time imaging of the nucleation and growth of the self-assembled layer was captured and studied via Scanning Tunneling Microscopy (STM), and further explored using computational methods.

Dynamic self-assembly of cobalt (II) octaethylporphyrin at the solution-solid interface

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.